This invention relates to infusion devices and more particularly to an improved autotransfusion device.
The term "autotransfusion", as used herein, refers to the infusion of a patient's own blood back into the patient. For example, during certain types of cardiac surgery, an extracorporeal circulating system is used which has a blood pump and blood oxygenator for assuming the functions of the heart and lungs. In such a system, the patient's blood is continuously reinfused. Also, during certain types of surgery, it is highly desirable to return the patient's own blood that would otherwise be lost, especially where the blood loss would be relatively great.
In the latter case, an autotransfusion set is generally used which has blood filtering and reservoir chambers, a suction device and pump for picking up the blood and supplying it to the filtering chamber, and an outlet at the reservoir chamber which is connected to a hypodermic cannula to return the filtered blood to the patient. While the pump must be continuously operated to provide a sufficient suction force for drawing blood from the suction tip into the filtering chamber, the pressure in the chamber should be limited to only that necessary to obtain an adequate rate of infusion to avoid undesirable effects on the patient from too high a pressure. In some cases, a pressure relief tube is connected between the filtering chamber and a control valve located in a monitoring console, which console may also include the control for the pump as well as other devices. This arrangement has the disadvantages of requiring an additional tube and its connections, additional set-up time, and, in general, complicating the apparatus. Also, an autotransfusion set of the type having a relief tube can only be used where equipment having a pressure control device connectable with the tube is available.
When the autotransfusion set is used to return blood loss during surgery, the rate of flow of blood into the autotransfusion set chamber varies considerably, for example, it can vary from zero to a relatively high rate of flow. For this reason, it has generally been found necessary to have an attendant continuously monitor the apparatus to insure that the line into the patient is continuously filled with blood in order to avoid the infusion of air into the patient and air embolisms. When the blood level in the reservoir does reach a predetermined low level, it is necessary for the attendant to manipulate a control to close off the reservoir from the patient. Also, in some cases, the pressure control valve may fail to provide close regulation, and/or has parts such as springs and adjustable parts which are subject to malfunction.